(ORDO NEWS) — The simple question “why is the snake so long” is actually very difficult to answer – but we will try.
A snake can have from 25 to 45 pairs of ribs, while a person has only 12. It is known that the number of vertebrae, muscles and ligaments that make up the body varies widely among different animals, but is always the same for representatives of the same species.
Obviously, there is a mechanism by which the expression of genes responsible for the composition and length of different parts of the body changes dramatically when a new species is formed.
This mechanism, as found by a group of scientists from the University of Gulbenkian in Portugal, lies in non-coding DNA – regions of the genome that do not code for proteins.
To study this question, the scientists did not study snakes, but mice with an unusually long body. An ordinary mouse has 13 pairs of ribs, while mutant mice from the Portuguese laboratory have all 24.
The reason for the mutation turned out to be the deactivation of the GDF11 gene, which, being active, blocks the work of another gene, OCT4, due to which extra vertebrae and ribs grow.
However, in snakes, the GDF11 gene is in order: why do they grow long? The answer lies in the non-coding DNA surrounding the OCT4 gene.
Initially, non-coding DNA was thought to have no function; it was even called “garbage”. In the last two decades, biologists have become convinced that this is far from being the case; in particular, non-coding DNA is able to “turn on” and “turn off” genes and manage the schedule of gene expression.
The scientists transplanted sections of the snake genome surrounding the OCT4 gene into normal mouse embryos and waited.
The embryos developed into mice with many extra vertebrae and ribs, confirming the theory that “junk” DNA is actually not junk at all and greatly affects gene expression.
Colleagues of Portuguese geneticists believe that the final proof that it’s all about non-coding DNA should be a snake with artificial non-coding DNA – one that “turns off” OCT4 in the early stages of development of other vertebrates.
If such a snake turns out to be short, the hypothesis about the role of non-coding DNA will be confirmed; however, it is difficult.
When a snake lays eggs, the embryos in them already have up to 26 pairs of ribs, and it is very difficult to obtain snake embryos at earlier stages of development.
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